I would say a relatively broad topic, with little to no information. The answer to the question is that more than 4 packers in a string were set safely, numerous times.
The way I would approach the topic, is as follows:
- determine if you need a hydraulic set, permanent or retrievable case hole or open hole and/or swellables
- determine if you require a zero bubble or not. Use this information when you check the device qualification provided by your vendor and/or further testing
- determine absolute and differential pressure requirements
- determine materials' and elastomers' requirements and compatibility with completion fluids and additives, produced fluids, gas lift if any, stimulation fluids if any and chemical injection fluids, if any
- run a stress analysis to determine stress points under different loads, including setting operation
- obtain the paker's envelope from your vendor and overlap the calculated points on the envelope. If they fall outside the envelope reiterate or introduce operational limits if possible to do so safely
- check the envelope in un-cemented pipe, just in case...
- as much as possible select a connection envelope similar to your tubing string, if not check the connection selected against your tubing string connection
- from a packer's construction point of view, the less parts, internal connections and moving parts, the better
- have a QA/QC plan in place until the device is delivered and accepted
- make up in sub-assemblies and bench test
- run a drag analysis, look at doglegs and confirm the distance between consecutive packers is sufficient so the string can negotiate and go through
- clean the well before running them in
- adjust the running speed based on your vendor"s historical experience and potential testing so you don't wash out the element
Finally, on depth know, I think you stand a good chance to set them safely.
Hope this helps,